Ubuntu is one of the most user friendly Debian based Linux distributions. It curently has a LTS version out, Ubuntu 14.04, codename Trusty Tahr. As of the older LTS 12.04(Precise Pangolin) both the server and desktop version will have support for 5 years. Meaning they will have security updates for 5 years. After 5 years it is wise to switch to the newer LTS release.